Dual taper fan-motor assembly

ABSTRACT

A motor-driven fan assembly includes a bracket which couples to a motor assembly and includes an outlet port. A shroud assembly defines a chamber and includes an inlet port. The shroud assembly is received on a bracket and a bearing-supported shaft is driven by the motor assembly and extends through the bracket and into the shroud assembly. At least one fan is coupled to the shaft and received in the chamber. The fan includes a plurality of curved blades positioned between a frustoconical lower cap and an opposed frustoconical upper cap. Rotation of the fan by the shaft results in turbulent air flow through the fan assembly. Dust is generally prevented from settling on the fan blades during operation, thereby preventing non-uniform dust buildup or breakup which may cause excessive vibration and reduce bearing and brush life.

TECHNICAL FIELD

The present invention is generally directed to motor assemblies. In particular, the present invention is directed to a fan assembly of a motor assembly which increases motor efficiency and air flow characteristics. Specifically, the present invention is related to a multi-stage fan assembly with working air fans having top and bottom tapers which promote efficiency and resist contaminant buildup.

BACKGROUND ART

Vacuum motors employing multi-stage tapered fans are used in many applications such as vacuum manipulators, packaging equipment, bag filling, cutting tables, appliances and exhaust air removal, to name just a few. Such vacuums designs generally include a cylindrical housing, or shroud, which encloses a pair of motor-driven working air fans rotating about an axis.

As shown in prior art FIG. 1, such designs draw air into a housing via an aperture A at the top axial center of the housing above a first stage fan B. The first stage fan includes a plurality of blades enclosed by a disc at the bottom and a frustoconical cap at the top. Channels are thereby defined between adjoining blades and, as the fan rotates, the air is accelerated through the channels in the circumferential and radially outward direction. The air is then directed into a second stage which includes a second stage fan C. The second stage fan may be generally identical to the first stage fan and includes a plurality of blades enclosed by a disc at the bottom and a frustoconical cap. Air is again accelerated through the channels defined by adjoining blades in the circumferential and radially outward direction. The housing provides an outlet located proximal the fan opposed to the aperture.

As is evident from FIG. 1, such fans may be tapered along the top surface defined by the frustoconical cap. In this manner the cross-sectional height of the fan becomes smaller as a function of radial distance from the axis of rotation. This in turn results in constriction in the channel volumes as a function of radial distance from the axis of rotation. This feature was provided to improve airflow properties and improve efficiency. While the tapering of the top frustoconical cap of such fans have been found to improve airflow, certain drawbacks persist. Specifically, assemblies of this nature have areas between the adjoining blades where airflow is virtually non-existent. As such, contaminants such as dust and debris collect in the rotating working air fans. This is particularly a concern when air drawn into the fan assembly carries a dust and water mixture such as would be seen in a wet/dry vacuum. Collection and retention of the contaminants in the fan causes the fan to become unbalanced. This adds stress to the rotating shaft and excess vibration which prematurely wears the motor brushes. Over time, these problems lead to bearing damage and eventual fan and/or motor assembly failure. Thus, while such fans are efficient in terms of airflow and have a small profile, the aforementioned drawbacks persist.

Therefore, there exists a need in the art for a fan assembly which minimizes dust and contaminate collection on the working air fans and therefore extends the life of the fan assembly.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a first aspect of the present invention to provide a motor fan which achieves improved efficiency.

Another aspect of the present invention is to provide a motor-driven fan assembly comprising a motor assembly, a bracket coupled to the motor assembly, the bracket including an outlet port, a shroud assembly which defines at least a chamber and includes an inlet port, the shroud assembly adapted to be secured to the bracket, a shaft rotated by the motor assembly, the shaft extending through the bracket and into the shroud assembly, and at least one fan coupled to the shaft and positioned in the chamber, wherein the at least one fan includes a plurality of curved blades positioned between an upper frustoconical cap and an opposed lower frustocinical cap, the at least one fan moving air from the inlet port to the outlet port.

Yet another aspect of the present invention is to provide a fan assembly comprising a shroud assembly that defines at least one chamber and includes an inlet port that communicates with the at least one chamber and an outlet port, a bracket coupled to the shroud assembly, the bracket having an opening aligned with the outlet port, the bracket having an aperture therethrough and adapted to receive a rotatable shaft therethrough, and at least one fan adapted to be coupled to the shaft and positioned in the at least one chamber, wherein rotation of the shaft causes air to be drawn into the inlet port and exhausted out the outlet port, and wherein the at least one fan includes a plurality of curved blades positioned between an angled upper cap and an opposed angled lower cap.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of the objects, techniques and structure of the invention, reference should be made to the following detailed description and accompanying drawings, wherein:

FIG. 1 is a sectional view of a prior art fan/motor assembly;

FIG. 2 is an end view of a fan/motor assembly made in accordance with the concepts of the present invention;

FIG. 3 is a sectional view of the fan/motor assembly made in accordance with the concepts of the present invention;

FIG. 4 is an exploded sectional view of the fan/motor assembly made in accordance with the concepts of the present invention;

FIG. 5 is a top plan view and partial breakaway view of an exemplary rotating fan;

FIG. 6 is a side plan view of an exemplary rotating fan; and

FIG. 7 is a top plan view of an exemplary stationary fan.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings and more particularly to FIGS. 2-4, it can be seen that a motor/fan assembly made in accordance with the invention is designated generally by the numeral 10. The motor/fan assembly 10 of the present invention includes a motor sub-assembly 11 and a fan sub-assembly 12. It should be appreciated that this disclosure is generally directed towards the fan sub-assembly, and thus the motor sub-assembly 11 may be of any suitable conventional construction. In one embodiment, the motor sub-assembly 11 includes a housing 13. The motor housing 13 may provide a commutator bracket which carries a concentrically positioned bearing 14 which receives a shaft 15 therein. The shaft 15 supports an armature 16 and a commutator 17 thereon, as well as a number of fans as will be hereinafter discussed. As is known in the art, these motor components interact to cause shaft 15 to selectively rotate and drive the working components of fan sub-assembly 12.

An end bracket 30 is provided on the end of motor sub-assembly 11 opposite the motor housing 13. End bracket 30 may be generally circular and is provided to enable fan components to be coupled to the motor sub-assembly 11. End bracket 30 includes an outer flange 32 which defines the radially outer surface thereof. A notched portion 34 may be provided circumferentially around outer flange 32. At least one outlet 36, in the form of a tangential horn, is provided in end bracket 30. While the outlet of the present embodiment faces a direction tangent to the central shaft axis, it should be appreciated that other outlet designs may be employed. For example, a plurality of radially or axially facing ports may be employed which achieve substantially the same results for exhausting air from fan sub-assembly 12.

The shaft 15, which is operatively coupled to the above mentioned motor elements, extends through and is supported by end bracket 30. Accordingly, end bracket 30 includes a support ring 38 which is formed with a generally cylindrical body 40, and a flange 42 that projects radially inward from cylindrical body 40. Flange 42 defines an axially oriented opening 44 which is sized to allow shaft 15 to extend therethrough. The cylindrical body 40 is adapted to receive a bearing 46 therein that in turn rotatably receives shaft 15 therethrough. Shaft 15 is thus supported by end bracket 30 via bearing 46, which allows for rotation therein. Various types of seals may be employed between the end bracket and the shaft to protect the bearing from moisture and dirt.

Fan sub-assembly 12, which is supported by the end bracket 30, includes a shroud assembly 52 which encloses a plurality of fans as will be hereinafter discussed. It should be appreciated that, while embodiments shown in FIGS. 3 and 4 employ two working air fans, any number might be employed, and multiple fans could be stacked in the manner disclosed below. Shroud assembly 52 includes a first shell 54 that is positioned at the axial end of fan sub-assembly 12, opposite the end bracket 30. First shell 54 includes an outer wall 56 which is substantially cylindrical and centered about the axis defined by shaft 15. Outer wall 56 terminates at a radiused edge 58 that transitions to a generally flat axially facing wall 60. Facing wall 60 is annular and extends radially inwardly from radiused edge 58. Facing wall 60 defines an axially centered inlet port 62. Inlet port 62 provides the opening through which working air enters fan sub-assembly 12.

Shroud assembly 52 further includes a second shell 70 that includes an outer wall 72 that is substantially cylindrical and centered about the axis defined by shaft 15. As shown in FIG. 3, outer wall 56 of first shell 54 is received over a portion of outer wall 72 and rests against a step 74. Step 74 acts as a stop, against which the rim of outer wall 56 rests. In this manner the first shell 54 is stacked atop the second shell 70. Outer wall 72 terminates at a chamfered edge 76 which transitions to an axially facing base wall 78. Base wall 78 is generally disc shaped and projects radially inward from outer wall 72. An opening 80 is provided at the concentric center of base wall 78. As is evident from FIG. 3, the first shell 54 and second shell 70 define a first chamber 82, access to which is provided at inlet port 62 and opening 80. Further, second shell 70 and end bracket 30 define a second chamber 84, access to which is provided at inlet port opening 80 and outlet 36.

As earlier discussed, shroud assembly 52 encloses a plurality of fans. First chamber 82 encloses a first working air fan 90, hereinafter first fan 90. First fan 90 includes lower cap 92 in the form of a frusto-conical disc. In other words, in cross-section, lower cap 92 includes a profile that is oriented at an angle other than 90 degrees relative to the axis defined by shaft 15. Lower cap 92 terminates at it's radial inner surface at a base 94, which is in the form of an axially facing disc. Base 94 is rotationally coupled to shaft 15 and, to that end, is provided with a central bore 96 that is sized to receive shaft 15 therethrough.

First fan 90 also includes an upper cap 98 in the form of a frusto-conical disc. In other words, in cross-section, upper cap includes a profile that is oriented at an angle other than 90 degrees relative to the axis defined by shaft 15. Upper cap 98 defines an aperture 100 that is centrally aligned with the axis defined by shaft 15. Aperture 100 is sized to be approximately the same diameter as inlet port 62. As is evident from FIGS. 4 and 6, upper cap 98 and lower cap 92 may include generally linear cross-sections. Further, it should be appreciated that the opposed caps 92 and 98 are oriented such that the distance therebetween grows smaller with radial distance away from the axis defined by shaft 15. Still further, in one or more embodiments lower cap 92 is, in cross section, a mirror image of upper cap 98.

As shown in FIG. 5, a plurality of blades 102 are secured between lower cap 92 and upper cap 98, each being disposed in a curved sunburst arrangement radiating outwardly towards outer wall 56. Each blade 102 includes a leading edge 104 that is spaced from shaft 15, thus defining a fan eye 106. Each blade 102 terminates proximate to the outer radial edge of lower cap 92 and upper cap 98 at a trailing edge 108. When shaft 15 rotates in a counter-clockwise direction, the blades 102 shown in FIG. 5 further define a leading surface 110 which is opposite a trailing surface 112, as will be discussed later in more detail. In one or more embodiments, the blade 102 may be coupled to upper and lower caps 92 and 98 by a plurality of stakes or rivets which are received in corresponding holes along caps 92 and 98. Each blade 102 is tapered at both the bottom and top. In other words, the height of blades 102 grows smaller as radial distance from shaft 15 increases. In embodiments where lower and upper caps 92 and 98 are linear, the height will correspondingly be reduced linearly as radial distance increases. Each adjoining blade 102 defines a channel 114 therebetween, that provides a path for airflow during fan operation.

First chamber 82 also encloses a stationary fan 116, carried by second shell 70. As seen in FIG. 7, stationary fan 116 includes a plurality of blades 118 which may be oriented in a sunburst arrangement radiating outwardly towards outer wall 56. A disc 120 is positioned along the top surface of blades 118 and includes a central bore 122 which allows shaft 15 to extend therethrough. Blades 118 extend radially inward from the outer radial edge of disc 120 and end at the central opening 80 of second shell 70.

The central opening 80 of second shell 70 communicates with a second working air fan130, hereinafter second fan 130, which is enclosed within second chamber 84. Second fan 130 may be substantially identical to first working air fan 104. Thus, second fan includes lower cap 132 in the form of a frusto-conical disc. In other words, in cross-section, lower cap 132 includes a profile that is oriented at an angle other than 90 degrees relative to the axis defined by shaft 15. Lower cap 132 terminates at it's radial inner surface at a base 134 in the form of an axially facing disc. Base 134 is rotationally coupled to shaft 15 and, to that end, is provided with a central bore 136 that is sized to receive shaft 15 therethrough.

Second fan 130 also includes an upper cap 138 in the form of a frusto-conical disc. In other words, in cross-section, upper cap 138 includes a profile that is oriented at an angle other than 90 degrees relative to the axis defined by shaft 15. Upper cap 138 defines an aperture 140 that is centrally aligned with the axis defined by shaft 15. Aperture 140 is sized to be approximately the same diameter as inlet port 80. As is evident from FIGS. 4 and 6, upper cap 138 and lower cap 132 may include generally linear cross-sections. Further, it should be appreciated that the opposed caps 132 and 138 are oriented such that the distance therebetween grows smaller with radial distance away from the axis defined by shaft 15. Still further, in one or more embodiments lower cap 132 is, in cross section, a mirror image of upper cap 138.

As shown in FIG. 5, a plurality of blades 142 are secured between lower cap 132 and upper cap 138, each being disposed in a curved sunburst arrangement radiating outwardly towards outer wall 72. Each blade 142 includes a leading edge 144 that is spaced from shaft 15, thus defining a fan eye 146. Each blade 142 terminates proximate to the outer radial edge of lower cap 132 and upper cap 138 at a trailing edge 148. When shaft 15 rotates in a counter-clockwise direction, the blades 142 of FIG. 5 further define a leading surface 150 and a trailing surface 152, as will be discussed later in more detail. In one or more embodiments, the blades 142 may be coupled to upper and lower caps 132 and 138 by a plurality of stakes or rivets (not shown) which are received in corresponding holes along caps 132 and 138. Each blade 142 is tapered along both the respective bottom and top edges. In other words, the height of blades 142 grow smaller as radial distance from shaft 15 increases. In embodiments where lower and upper caps 132 and 138 are linear, the height will correspondingly be reduced linearly as radial distance increases. Each adjoining blade 142 defines a channel 154 therebetween, that provides a path for airflow during fan operation. second working air fan 142 includes a base 144 in the form of a disc.

In the present embodiment, the aforementioned fans 90 and 130 are spaced and coupled to the shaft 15 by a plurality of elements. A T-spacer 160 extends inwardly through opening 44 in support ring 38 and bears against or is adjacent to an inner race of bearing 46. T-spacer 160 may have a generally T-shaped cross section to provide an enlarged transverse surface against which the base 146 of second fan 130 may bear. Positioned between fans 90 and 130 is an I-spacer 162 which is received on shaft 15 and may have a generally I-shaped cross section. A washer 164 may be provided at the end of shaft 15 that includes a notched portion 166 that rests against a corresponding notched portion 168 of shaft 15. A nut 170 may be provided at the end of shaft 15 that may be tightened against washer 164 which in turn bears against base 94 of first working air fan 90. This in turn clamps together the inner race of the bearing 46, T-spacer 160, I-spacer 162, fans 90 and 130 and washer 164 so that all turn as one unit with the shaft 15 as it is driven by the motor sub-assembly 11. In this manner, when shaft 15 rotates counter-clockwise, air is drawn into first chamber 82 via inlet port 62. Air is then drawn into eye 106 and is urged radially outward by blades 102. Once the air is ejected radially outwardly past blades 102, blades 118 of the stationary fan 116 direct the air flow radially inward toward opening 80. As is evident from FIG. 3, opening 80 directs the air flow into second chamber 84. As second fan 130 rotates, blades 142 again urge the air radially outward. Because of the pressure differential between the outside atmosphere and the second chamber 84, the air exits second chamber 84 via outlet port 36. Thus, as described above, air is drawn into inlet port 62 and out of outlet port 36 upon counter-clockwise rotation of shaft 15.

Of particular concern in such fans is the collection of dust and other particles within the working air fans. The profile of fan blades 102 and 142 in the configuration disclosed greatly reduces contaminants from sticking to fan blades. Indeed, the dual taper design could be used in a single fan configuration. It has been found that in conventional multi-stage fans, dust and debris tend to stick to the leading surface 110 or 150 as air travels radially outward from the eye 106 or 146 of the fan. By reducing the height of the blades 102 and 142 and correspondingly including angled lower caps 92/132 and upper caps 98/138 so that the blades are tapered at both sides, the cross sectional area of channels 114 and 154 are thus reduced. The reduction in channel area of the present invention is thus reduced more quickly than in a prior art fan. Consequently, the particles in the air are accelerated faster than a traditional fan. Because the air is accelerated faster as it travels radially outward, any particles or contaminates in the air are ejected from the fan and not given an opportunity to stick to the leading surface 110 or 150. In other words, the channels formed by the dual taper blades and the frusto-conical caps generate a continually increasing pressure gradient from where the air enters the channels proximal the inlet to where the air exits the channels at the outer radial edges of the caps. Such a configuration is believed to generate turbulence within the entire channel, thus preventing accumulation of any debris. Thus, when such a dual blade taper is employed with a multi-stage working air fan design, the incidence of fan contamination is greatly reduced. This in turn leads to increased fan and bearing life. Specifically, uneven contaminate buildup, or buildup which suddenly breaks away from the blades, can cause vibration, which degrades bearing life. By preventing contaminates from sticking to the blades, this vibration is limited and bearing life is increased.

Thus, it can be seen that the objects of the invention have been satisfied by the structure presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims. 

1. A motor-driven fan assembly, comprising: a motor assembly; a bracket coupled to said motor assembly, said bracket including an outlet port; a shroud assembly which defines at least a chamber and includes an inlet port, said shroud assembly adapted to be secured to said bracket; a shaft rotated by said motor assembly, said shaft extending through said bracket and into said shroud assembly; and at least one fan coupled to said shaft and positioned in said chamber, wherein said at least one fan includes a plurality of curved blades positioned between an upper frustoconical cap and an opposed lower frustoconical cap, said at least one fan moving air from said inlet port to said outlet port.
 2. The fan assembly according to claim 1, wherein said blades are disposed between said caps in a curved sunburst arrangement radiating radially outwardly.
 3. The fan assembly according to claim 1, wherein said upper frustoconical cap further comprises a disc shaped base secured at its radial outer edge to a radial inner edge of said lower frustoconical cap.
 4. The fan assembly according to claim 3, wherein said base includes a central aperture adapted to receive said shaft therethrough.
 5. The fan assembly according to claim 1, wherein said upper frustoconical cap is substantially a mirror image in cross section of said lower frustoconical cap.
 6. The fan assembly according to claim 5, wherein said shroud assembly further comprises a first shell and a second shell, said first shell being secured to said second shell and said second shell secured to said bracket, a first chamber formed between said first shroud and said second shroud, and a second chamber formed between said second shroud and said bracket.
 7. The fan assembly according to claim 6, further comprising: a stationary fan disposed between said first chamber and said second chamber; and a second fan constructed substantially the same as said first fan and coupled to said shaft and positioned in said second chamber.
 8. The fan assembly according to claim 1, wherein said upper frustoconical cap comprises an aperture extending therethrough and when said shaft rotates, air is drawn through said aperture and radially outward across said blades.
 9. A fan assembly, comprising: a shroud assembly that defines at least one chamber and includes an inlet port that communicates with said at least one chamber and an outlet port; a bracket coupled to said shroud assembly, said bracket having an opening aligned with said outlet port, said bracket having an aperture therethrough and adapted to receive a rotatable shaft therethrough; and at least one fan adapted to be coupled to the shaft and positioned in said at least one chamber, wherein rotation of the shaft causes air to be drawn into said inlet port and exhausted out said outlet port, and wherein said at least one fan includes a plurality of curved blades positioned between an angled upper cap and an opposed angled lower cap.
 10. The fan assembly according to claim 9, wherein each said blade is disposed between said caps in a curved sunburst arrangement radiating radially outwardly.
 11. The fan assembly according to claim 9, wherein said upper angled cap further includes a disc-shaped base secured at its radial outer edge to a radial inner edge of said lower angled cap.
 12. The fan assembly according to claim 11, wherein said base includes a central aperture adapted to receive the shaft therethrough.
 13. The fan assembly according to claim 12, wherein said upper angled cap is a mirror image in cross section of said lower angled cap.
 14. The fan assembly according to claim 9, wherein said shroud assembly further comprises a first shell and a second shell, said first shell being secured to said second shell and said second shell secured to said bracket, said first chamber being formed between said first shell and said second shell, said second chamber being formed between said second shell and said bracket, and wherein said fan assembly further comprises a second fan, substantially the same as said first fan, and adapted to be coupled to the shaft and received in said second chamber.
 15. The fan assembly according to claim 14, further comprising a stationary fan carried by said second shell and including a plurality of curved blades and a disc having a central bore, wherein air expelled by said first fan is directed by said stationary fan into said second fan. 